The present invention relates generally to tunable inductors, and more particularly, to microelectromechanical systems (MEMS) switched tunable inductors.
Tunable inductors can find application in frequency-agile radios, tunable filters, voltage controlled oscillators, and reconfigurable impedance matching networks. The need for tunable inductors becomes more critical when optimum tuning or impedance matching in a broad frequency range is desired. Both discrete and continuous tuning of passive inductors using micromachining techniques have been reported in the literature.
Discrete tuning of inductors is usually achieved by changing the length or configuration of a transmission line using micromachined switches. The incorporation of switches in the body of the tunable inductor increases the resistive loss and hence reduces the quality factor (Q). Alternatively, continuous tuning of inductors may be realized by displacing a magnetic core, changing the permeability of the core, or using movable structures with large traveling range. Although significant tuning has been reported using these methods, the fabrication or the actuation techniques are complex, making the on-chip implementation of the tunable inductors difficult. In addition, Q of the reported tunable inductors is not sufficiently high for many wireless and RF integrated circuit applications.
Therefore, there is a need for high-performance small form-factor tunable inductors. Also, to overcome the shortcomings of prior art tunable inductors, an improved design and micro-fabrication method for tunable inductors is necessary.